Horseshoe Crabs
Many kinds of fossils other than plants and insects are found in the Mazon Creek-Braidwood area of Illinois, and among them are the horseshoe crabs. These marine animals were much like their present-day relatives and must have lived in shallow seas just offshore from Coal Age forests. A relatively few specimens have been found in Illinois. All are of Pennsylvanian age and came from the Mazon Creek area.
See horseshoe crabs: plate 21 (center right of image).
Common Types of Illinois Fossils
The printed version of Guide for Beginning Fossil Hunters can be purchased from the Shop ISGS Web site.
Updated 09/23/2011 SLD